Diabetic foot infections (DFIs) are a frequent and serious complication of diabetes mellitus (DM) and are the world leading cause of non-traumatic lower limb amputation (Jeffcoate W J, et al. 2003. Lancet 361:1545-1551). In current clinical practice, the treatment of DFIs includes debridement and systemic antibiotics (see, e.g., Lipsky B A, et al. 2004. Clin Infect Dis. 39:885-910). Nonetheless, because of deficient vascularization and the local microenvironment, antibiotic concentrations are many times sub-therapeutical (Lipsky B A, et al. 2009. Clin Infect Dis. 49:1541-1549). Moreover, the increasing incidence of multidrug resistant organisms, such as methicillin-resistant Staphylococcus aureus, as well as pan-drug-resistant non-fermenting negative bacilli, is threatening the outcome in increasing numbers of community and hospitalized patients (Mendes J J, et al. 2012. Diabetes Res Clin Pract. 95(1):153-161; Tascini C, et al. 2011. Diabetes Res Clin Pract 94 (1):133-139). Accordingly, there remains a need to identify new strategies for the treatment, control, and management of DFIs.
Topical treatment provides the advantages of avoiding systemic adverse effects, providing increased target site concentration, and allowing the use of agents not available for systemic therapy. Mechanical debridement improves topical treatment because it reduces the bio-burden of bacteria present and also opens a time-dependent therapeutic window for topical antimicrobial therapy (TAT) (Wolcott R D, et al. 2010. J Wound Care 19:320-328). Nevertheless, to date, no TAT agent has been proven to be effective for treating DFI (Nelson E A, et al. 2006. Diabet Med 23:348-359).
Bacteriophage (phage) are viruses that specifically infect and lyse bacteria. Phage therapy, a method of using whole phage viruses for the treatment of bacterial infectious diseases, was introduced in the 1920s by Felix d'Herelle. With the development of antibiotics in the 1940s, however, interest in phage-based therapeutics declined in the Western world. One of the most important factors that contributed to this decline was the lack of standardized testing protocols and methods of production. The failure to develop industry wide standards for the testing of phage therapies interfered with the documentation of study results, leading to a perceived lack of efficacy, as well as problems of credibility, regarding the value of phage therapy. Another problem in phage production related to the purity grade of commercial preparations of phage, with preparations containing undesired bacterial components, e.g., endotoxins. Accordingly, adverse events were often associated with the preparations, particularly in patients receiving them intravenously.
Nevertheless, in Eastern Europe and the former Soviet Union, where access to antibiotics was limited, the development and use of phage therapy continued jointly with, or in place of, antibiotics. Further, with the rise of antibiotic resistant strains of many bacteria, interest in phage-based therapeutics has returned in the Western world. That is, even though novel classes of antibiotics may be developed, the prospect that bacteria will eventually develop resistance to the new drugs has intensified the search for non-chemotherapeutic means for controlling, preventing, and treating bacterial infections.
Lytic bacteriophage, especially when complemented by adequate mechanical debridement, offer a solution to treating DFIs, e.g., for use as novel TAT agents. Lytic bacteria can offer the advantages of specificity and efficiency in lysing pathogenic bacteria, even those associated with multidrug resistance (Rossney A S, et al. 1994. J Hosp Infect 26:219-234.) Further advantages can include absence of pathogenicity to man and animals (Burrowes B, et al. 2011. Expert Rev Anti Infect Ther 9:775-785), antibacterial activity against bacteria in biofilms, and activity in microaerophilic environments, even with high bacterial load (Azeredo J, et al. 2008. Curr Pharm Biotechnol 9:261-266), as well as the generally accepted safety of bacteriophage therapy in some parts of the world (Sulakvelidze A, et al., 2001, Antimicrob Agents Chemother. 45(3): 649-659). Recent animal trials of bacteriophage therapy have demonstrated its potential to heal or improve skin bacterial diseases, both in internal (McVay C S, et al. 2007. Antimicrob Agents Chemother 51:1934-1938) and external applications (Soothill J S. 1994. Burns 20:209-211; Wills Q F, et al. 2005. Antimicrob Agents Chemother 49:1220-1221). However, there is little published evidence supporting the use of bacteriophage to cure infections established for longer than a few hours (Ryan E M, et al. 2011 J Pharm Pharmacol 63:1253-1264).
In particular, phage cocktails may provide advantages to the use of phages individually, e.g., to increase the lytic activity against a particular bacterial strain, and to decrease the possibility of emergence of bacteria resistant to an individual bacteriophage. That is, different bacteriophage can be mixed as cocktails to broaden their properties, preferably resulting in a collectively greater antibacterial spectrum of activity e.g., an expanded host range, to which development of resistance is less likely. Nonetheless, to date, few phage cocktails exist with antimicrobial activity against different bacteria, possibly because of the difficulty in combining different specificities of bacteriophage while maintaining storage stability.
There is therefore a need to develop novel phage products as therapeutic and/or prophylactic agents for use in vivo against pathogenic bacteria. There also is a need for better treatments, particularly topical treatments, for DFIs. In particular, there is a need for bacteriophage cocktails capable of lysing bacteria responsible for DFIs, including Staphylococcus aureus, Pseudomonas aeruginosa, and/or Acinetobacter baumannii. This application addresses this and other needs.